Magnetic disk, method of accessing magnetic disk device, and recording medium storing disk access control program for magnetic disk device

ABSTRACT

A magnetic disc apparatus according to the present invention is one which is provided with a host interface unit  2  which controls the interface connected to a host apparatus  1 , a command administrating unit  3 , a position information administrating unit  4 , a control unit  5  which controls the whole operation of a magnetic disc apparatus  9 , a buffer memory  6  which temporarily stores data, a read/write control unit  7  and a magnetic disc  8.    
     The magnetic disc apparatus thus constituted can enhance the data transmission efficiency even when accessing to plural systems of large capacity successive data are carried out.

TECHNICAL FIELD

The present invention relates to a magnetic disc apparatus and, moreparticularly, to magnetic disc apparatus which accesses plurality oflarge capacity successive data, and a disc access method for themagnetic disc apparatus. Further, the invention relates to a recordingmedium having recorded a program for a disc access control for amagnetic disc apparatus.

BACKGROUND ART

In computer systems which perform control and administration of OAapparatuses or industrial apparatuses, accompanying with an increase inhandling information data, a large capacity memory has been required forrecording those information data. As a large capacity memory devicesatisfying such requirements, a magnetic disc apparatus employing amagnetic disc as recording medium has been widely used.

By the way, in transmitting files between a magnetic disc apparatus anda host apparatus connected externally of the magnetic disc apparatus, itis a basic operation that the magnetic disc apparatus commences accessto the magnetic disc in the magnetic disc apparatus after receiving acommand issued from the host apparatus.

When a command and a command parameter are transmitted at the same timefrom the host apparatus, the magnetic disc apparatus calculates at whichposition on the magnetic disc the data the host apparatus has requiredan access physically exists, makes the head seek a track on the magneticdisc in the magnetic disc apparatus according to the calculated result,thereby to perform reading out or writing in from/into the data requiredby the host apparatus.

Hereinafter, such a magnetic disc apparatus will be described,particularly on the operation thereof with reference to drawings.

FIG. 7 is a diagram illustrating an operation of the magnetic discapparatus, and particularly, a processing performed on the magneticdisc, when the host apparatus accesses two large capacity successivedata located apart from each other in the magnetic disc apparatus at thesame time.

In FIG. 7, file (m−1)′, m, m′ and m+1constitute a part of large capacitysuccessive data A, and file (n−1)′, n, n′ and n+1 constitute a part oflarge capacity successive data B.

Further, file (m−1)′ and file m locate on track M, file m′ and file m+1locate on track M+1, file (n−1) and file n locate on track N, and filen′ and file n+1 locate on track N+1. Each file has the size that isequal to the data length which is handled at one time command by thehost apparatus.

While when the host apparatus accesses a large capacity successive data,the host apparatus has only to issue commands for accessing files inchronological order of the successive files, when the host apparatusaccesses two large capacity successive data at the same time, the hostapparatus has to issue commands for accessing respective files in thelarge capacity successive data A and commands for accessing respectivefiles in the large capacity successive data B, alternately, at aconstant period (band). These commands are shown in FIG. 8.

In this case, as shown in FIG. 8, the magnetic disc apparatus interpretsthe content of the command each time when it receives the issuedcommand, and calculates the positional information at which physicallocation the demanded data locates physically on the magnetic disc fromthe command parameter thereby to carry out accessing to the data on themagnetic disc.

That is, in the magnetic disc apparatus, accessing to the large capacitysuccessive data A and accessing to the large capacity successive data Bare carried out alternately and successively.

To be concrete, as shown in FIG. 7, accessing to the magnetic disc iscarried out in the order of access 1 to the file m and the file m′, seek1 for executing access 2 to the file n and the file n′, the access 2 tothe file n and the file n′, seek 2 for executing access 3 to the filem+1, the access 3 to the file m+1, seek 3 for executing access 4 to thefile n+1, and the access 4 to the file n+1.

However, in the conventional magnetic disc apparatus, though accessingto files respectively constituting each of two large capacity successivedata are carried out alternatively, and it is possible to predict aphysical location from which accessing to data on the optical disc isstarted, it is impossible to start accessing to respective files until acommand is issued from the host apparatus. In other words, the magneticdisc should arise an idle state in which nothing is performed to themagnetic disc during a period from the completion of an access to a fileup to starting of a seek for carrying out an access to next file.

That is, when the host apparatus accesses a plurality of large capacitysuccessive data at the same time, even though there is a highpossibility of performing an access to data whose access startingposition on the magnetic disc can be predicted, the magnetic discapparatus stops accessing to the magnetic disc and enters a waitingstate (the idle state) after completing the accessing to the file nowbeing processed, and the idle state continues until a next command isreceived. When receiving the next command, the magnetic disc apparatusinterprets the received command, calculates location information fromthe command parameter, and seeks the track in which data is present, andthereafter, starts accessing to the data.

In this way, when the host apparatus accesses a plurality of largecapacity successive data at the same time, there should arise an idlestate where no access is performed to the magnetic disc, thereby noimprovement in the data transfer efficiency.

The present invention is directed to solve the above described problem,and has for its object to provide a magnetic disc apparatus which doesnot reduce the data transfer efficiency between the magnetic disc and abuffer memory even when accessing to plural systems of large capacitysuccessive data are carried out, to provide a disc access method for themagnetic disc apparatus, which enables the above-described disc access,and further, to provide a recording medium having recorded a disc accesscontrol program for a magnetic disc apparatus.

DISCLOSURE OF THE INVENTION

According to a first aspect of the present invention, there is provideda magnetic disc apparatus which can read out or write into various kindsof information data by accessing a magnetic disc employed as a recordingmedium, wherein when a host apparatus connected externally to themagnetic disc apparatus, performs an access to each of plural systemsconstituting large capacity successive data, which systems are locatedapart from each other in the magnetic disc apparatus, the magnetic discapparatus stores a record of commands at the same time when the hostapparatus issues commands for accessing the respective systems to themagnetic disc apparatus, compares a new received command with the storedrecord of commands to detect continuity of commands against therespective systems every time when it receives a new command issued fromthe host apparatus, and preserves location information indicatingphysical location on the magnetic disc at which data to be accessed foreach of the plural systems locate, and in which apparatus a systempreserving the location information starts data accessing to themagnetic disc by employing the location information when the magneticdisc apparatus receives a command issued from the host apparatus.

According to the present invention, while accessing large capacitysuccessive data on a magnetic disc, the time required for interpreting acommand after receiving the command can be reduced, as well as the timefrom the completion of an access to one system to the start of an accessto next system can be shortened, thereby the data transmissionefficiency is enhanced.

According to a second aspect of the present invention, there is provideda magnetic disc apparatus which can read out or write into various kindsof information data by accessing a magnetic disc employed as a recordingmedium, wherein when a host apparatus connected externally to themagnetic disc apparatus, performs an access to each of plural systemsconstituting large capacity successive data, which systems are locatedapart from each other in the magnetic disc apparatus, the magnetic discapparatus stores a record of commands at the same time when the hostapparatus issues commands for accessing the respective systems to themagnetic disc apparatus, compares a new received command with the storedrecord of commands to detect continuity of commands against therespective systems every time when it receives a new command issued fromthe host apparatus, and seeks a magnetic head employed in data access,to a track on the magnetic disc at which data of a system which issupposed to be accessed by the next command locate, without waitingreceiving of the next command when the accessing to the data on themagnetic disc at which the respective system data locate is completed.

According to the present invention, by that a seeking of a magnetic headto a track on which data which is supposed to be accesses next iscarried out at the conclusion of access to data, the time from thereceiving of a command to the starting of an access to the requesteddata while accessing a large capacity successive data on a magnetic discis reduced, thereby the time from the completion of an access to onesystem to the starting of an access to the next system is shortened andthe data transfer efficiency is enhanced.

According to a third aspect of the present invention, there is provideda magnetic disc apparatus which can read out or write into various kindsof information data by accessing a magnetic disc employed as a recordingmedium, wherein when a host apparatus connected externally to themagnetic disc apparatus, performs an access to each of plural systemsconstituting large capacity successive data, which systems are locatedapart from each other in the magnetic disc apparatus, the magnetic discapparatus stores a record of commands at the same time when the hostapparatus issues commands for accessing the respective systems to themagnetic disc apparatus, compares a new received command with the storedrecord of commands to detect continuity of commands against therespective systems every time when it receives a new command issued fromthe host apparatus, and performing data access, to a track on themagnetic disc at which data of a system which is supposed to be accessedby the next command locate, without waiting receiving of the nextcommand when the accessing to the data on the magnetic disc at which therespective system data locate is completed.

According to the present invention, by that the data access is startedby seeking a magnetic head to a track on which the data which issupposed to be accessed next exists, the time from the receiving of acommand to completing the access of the requested data while accessing alarge capacity successive data on a magnetic disc is reduced, therebythe time from the completion of an access to one system to thecompletion of an access to the next system is shortened and the datatransfer efficiency is enhanced.

According to a fourth aspect of the present invention, there is provideda magnetic disc apparatus of the second aspect or the third aspect,which stops seeking of a magnetic head to a track on the magnetic disc,in which the predicted system locates, in a case where a command isissued from the host apparatus and the content of the command is not anaccess to data of the system that is predicted, during the seekingoperation that is being performed in the magnetic disc apparatus beforereceiving the command from the host apparatus.

According to the present invention, in a case where a command to asupposed system is received during the seeking operation and thatcommand is one which accesses not to the supposed system but to anothersystem, the seeking operation to the supposed system is immediatelyhalted, and it is transited to the interpretation of the receivedcommand to initiate an access to the requested system, thereby anincrease in the access starting time to the system that is requested bythe command even when prediction was erroneously performed.

According to a fifth aspect of the present invention, there is provideda magnetic disc apparatus of the third aspect which stops accessing tothe data on the magnetic disc in which the supposed system exists, in acase where a command is issued from the host apparatus and the contentof the command is not an access to data of the system that is predicted,during the data accessing that is being performed in the magnetic discapparatus before receiving the command from the host apparatus.

According to the present invention, in a case where a command to asupposed system is received during the seeking operation and thatcommand is one which accesses not to the supposed system but to anothersystem, the accessing to the supposed system is immediately halted, andit is transited to the interpretation of the received command toinitiate an access to the requested system, thereby an increase in theaccess starting time to the system that is requested by the command isrestrained even when prediction was erroneously performed.

According to a sixth aspect of the present invention, there is provideda disc access method for a magnetic disc apparatus which apparatus canread out or write into various kinds of information data by accessing amagnetic disc employed as a recording medium, wherein when a hostapparatus connected externally to the magnetic disc apparatus, performsan access to each of plural systems constituting large capacitysuccessive data, which systems are located apart from each other in themagnetic disc apparatus, the magnetic disc apparatus stores a record ofcommands at the same time when the host apparatus issues commands foraccessing the respective systems to the magnetic disc apparatus,compares a new received command with the stored record of commands todetect continuity of commands against the respective systems every timewhen it receives a new command issued from the host apparatus, andpreserves location information indicating physical location on themagnetic disc at which data to be accessed for each of the pluralsystems locate, and in which apparatus a system preserving the locationinformation starts data accessing to the magnetic disc by employing thelocation information when the magnetic disc apparatus receives a commandissued from the host apparatus.

According to the present invention, while accessing large capacitysuccessive data on a magnetic disc, the time required for interpreting acommand after receiving the command can be reduced, as well as the timefrom the completion of an access to one system to the start of an accessto next system can be shortened, thereby the data transmissionefficiency is enhanced.

According to a seventh aspect of the present invention, there isprovided a disc access method for magnetic disc apparatus which can readout or write into various kinds of information data by accessing amagnetic disc employed as a recording medium, wherein when a hostapparatus connected externally to the magnetic disc apparatus, performsan access to each of plural systems constituting large capacitysuccessive data, which systems are located apart from each other in themagnetic disc apparatus, the magnetic disc apparatus stores a record ofcommands at the same time when the host apparatus issues commands foraccessing the respective systems to the magnetic disc apparatus,compares a new received command with the stored record of commands todetect continuity of commands against the respective systems every timewhen it receives a new command issued from the host apparatus, and seeksa magnetic head employed in data access, to a track on the magnetic discat which data of a system which is supposed to be accessed by the nextcommand locate, without waiting receiving of the next command when theaccessing to the data on the magnetic disc at which the respectivesystem data locate.

According to the present invention, by that a seeking of a magnetic headto a track on which data which is supposed to be accesses next exists iscarried out at the conclusion of access to data, the time from thereceiving of a command to the starting of an access to the requesteddata while accessing a large capacity successive data on a magnetic discis reduced, thereby the time from the completion of an access to onesystem to the starting of an access to the next system is shortened andthe data transfer efficiency is enhanced.

According to an eighth aspect of the present invention, there isprovided a disc access method for a magnetic disc apparatus which canread out or write into various kinds of information data by accessing amagnetic disc employed as a recording medium, wherein when a hostapparatus connected externally to the magnetic disc apparatus, performsan access to each of plural systems constituting large capacitysuccessive data, which systems are located apart from each other in themagnetic disc apparatus, the magnetic disc apparatus stores a record ofcommands at the same time when the host apparatus issues commands foraccessing the respective systems to the magnetic disc apparatus,compares a new received command with the stored record of commands todetect continuity of commands against the respective systems every timewhen it receives a new command issued from the host apparatus, andperforming data access, to a track on the magnetic disc at which data ofa system which is supposed to be accessed by the next command locate,without waiting receiving of the next command when the accessing to thedata on the magnetic disc at which the respective system data locate.

According to the present invention, by that the data access is startedby seeking a magnetic head to a track on which the data which issupposed to be accessed next exists, the time from the receiving of acommand to completing the access of the requested data while accessing alarge capacity successive data on a magnetic disc is reduced, therebythe time from the completion of an access to one system to thecompletion of an access to the next system is shortened and the datatransfer efficiency is enhanced.

According to a ninth aspect of the present invention, there is provideda disc access method for a magnetic disc apparatus of the seventh aspector the eighth aspect, which stops seeking of a magnetic head to a trackon the magnetic disc, in which the predicted system locates, in a casewhere a command is issued from the host apparatus and the content of thecommand is not an access to data of the system that is predicted, duringthe seeking operation that is being performed in the magnetic discapparatus before receiving the command from the host apparatus.

According to the present invention, in a case where a command to asupposed system is received during the seeking operation and thatcommand is one which accesses not to the supposed system but to anothersystem, the seeking operation to the supposed system is immediatelyhalted, and it is transited to the interpretation of the receivedcommand to initiate an access to the requested system, thereby anincrease in the access starting time to the system that is requested bythe command even when prediction was erroneously performed.

According to a tenth aspect of the present invention, there is provideda disc access method for a magnetic disc apparatus of the eighth aspectwhich stops accessing to the data on the magnetic disc in which thesupposed system exists, in a case where a command is issued from thehost apparatus and the content of the command is not an access to dataof the system that is predicted, during the data accessing that is beingperformed in the magnetic disc apparatus before receiving the commandfrom the host apparatus.

According to the present invention, in a case where a command to asupposed system is received during the seeking operation and thatcommand is one which accesses not to the supposed system but to anothersystem, the accessing to the supposed system is immediately halted, andit is transited to the interpretation of the received command toinitiate an access to the requested system, thereby an increase in theaccess starting time to the system that is requested by the command evenwhen prediction was erroneously performed.

According to an eleventh aspect of the present invention, there isprovided a recording medium having recorded a magnetic disc recordingapparatus control program, which has recorded a program concerning adisc access method for a magnetic disc apparatus, which apparatus canread out or write into various kinds of information data by accessing amagnetic disc employed as a recording medium, wherein when a hostapparatus connected externally to the magnetic disc apparatus, performsan access to each of plural systems constituting large capacitysuccessive data, which systems are located apart from each other in themagnetic disc apparatus, the magnetic disc apparatus stores a record ofcommands at the same time when the host apparatus issues commands foraccessing the respective systems to the magnetic disc apparatus,compares a new received command with the stored record of commands todetect continuity of commands against the respective systems every timewhen it receives a new command issued from the host apparatus, andpreserves location information indicating physical location on themagnetic disc at which data to be accessed for each of the pluralsystems locate, and in which apparatus a system preserving the locationinformation starts data accessing to the magnetic disc by employing thelocation information when the magnetic disc apparatus receives a commandissued from the host apparatus.

According to the present invention, while accessing large capacitysuccessive data on a magnetic disc, the time required for interpreting acommand after receiving the command can be reduced, as well as the timefrom the completion of an access to one system to the start of an accessto next system can be shortened, thereby the data transmissionefficiency is enhanced.

According to a twelfth aspect of the present invention, there isprovided a recording medium having recorded a magnetic disc apparatuscontrol program, which has recorded a program concerning a disc accessmethod for a magnetic disc apparatus, which apparatus can read out orwrite into various kinds of information data by accessing a magneticdisc employed as a recording medium, wherein when a host apparatusconnected externally to the magnetic disc apparatus, performs an accessto each of plural systems constituting large capacity successive data,which systems are located apart from each other in the magnetic discapparatus, the magnetic disc apparatus stores a record of commands atthe same time when the host apparatus issues commands for accessing therespective systems to the magnetic disc apparatus, compares a newreceived command with the stored record of commands to detect continuityof commands against the respective systems every time when it receives anew command issued from the host apparatus, and seeks a magnetic heademployed in data access, to a track on the magnetic disc at which dataof a system which is supposed to be accessed by the next command locate,without waiting receiving of the next command when the accessing to thedata on the magnetic disc at which the respective system data locate.

According to the present invention, by that a seeking of a magnetic headto a track on which data which is supposed to be accesses next exists iscarried out at the conclusion of access to data, the time from thereceiving of a command to the starting of an access to the requesteddata while accessing a large capacity successive data on a magnetic discis reduced, thereby the time from the completion of an access to onesystem to the starting of an access to the next system is shortened andthe data transfer efficiency is enhanced.

According to a thirteenth aspect of the present invention, there isprovided a recording medium having recorded a magnetic disc apparatuscontrol program, which has recorded a program concerning a disc accessmethod for a magnetic disc apparatus, which apparatus can read out orwrite into various kinds of information data by accessing a magneticdisc employed as a recording medium, wherein when a host apparatusconnected externally to the magnetic disc apparatus, performs an accessto each of plural systems constituting large capacity successive data,which systems are located apart from each other in the magnetic discapparatus, the magnetic disc apparatus stores a record of commands atthe same time when the host apparatus issues commands for accessing therespective systems to the magnetic disc apparatus, compares a newreceived command with the stored record of commands to detect continuityof commands against the respective systems every time when it receives anew command issued from the host apparatus, and performing data access,to a track on the magnetic disc at which data of a system which issupposed to be accessed by the next command locate, without waitingreceiving of the next command when the accessing to the data on themagnetic disc at which the respective system data locate.

According to the present invention, by that the data access is startedby seeking a magnetic head to a track on which the data which issupposed to be accessed next exists, the time from the receiving of acommand to completing the access of the requested data while accessing alarge capacity successive data on a magnetic disc is reduced, therebythe time from the completion of an access to one system to thecompletion of an access to the next system is shortened and the datatransfer efficiency is enhanced.

According to a fourteenth aspect of the present invention, there isprovided a recording medium having recorded a magnetic disc apparatuscontrol program, which has recorded a program concerning a disc accessmethod for a magnetic disc apparatus, of the twelfth aspect or thethirteenth aspect, which stops seeking of a magnetic head to a track onthe magnetic disc, in which the predicted system locates, in a casewhere a command is issued from the host apparatus and the content of thecommand is not an access to data of the system that is predicted, duringthe seeking operation that is being performed in the magnetic discapparatus before receiving the command from the host apparatus.

According to the present invention, in a case where a command to asupposed system is received during the seeking operation and thatcommand is one which accesses not to the supposed system but to anothersystem, the seeking operation to the supposed system is immediatelyhalted, and it is transited to the interpretation of the receivedcommand to initiate an access to the requested system, thereby anincrease in the access starting time to the system that is requested bythe command even when prediction was erroneously performed.

According to a fifteenth aspect of the present invention, there isprovided a recording medium having recorded a magnetic disc apparatuscontrol program, which has recorded a program concerning a disc accessmethod for a magnetic disc apparatus, of the thirteenth aspect whichstops accessing to the data on the magnetic disc in which the supposedsystem exists, in a case where a command is issued from the hostapparatus and the content of the command is not an access to data of thesystem that is predicted, during the data accessing that is beingperformed in the magnetic disc apparatus before receiving the commandfrom the host apparatus.

According to the present invention, in a case where a command to asupposed system is received during the seeking operation and thatcommand is one which accesses not to the supposed system but to anothersystem, the accessing to the supposed system is immediately halted, andit is transited to the interpretation of the received command toinitiate an access to the requested system, thereby an increase in theaccess starting time to the system that is requested by the command evenwhen prediction was erroneously performed.

According to a sixteenth aspect of the present invention, there isprovided a magnetic disc apparatus which can read out or write intovarious kinds of information data by accessing a magnetic disc employedas a recording medium, which comprises: a buffer memory which can storea plurality of data per one command which is transferred between thehost apparatus and the magnetic disc apparatus in response to thecommands issued from the host apparatus which is connected externally tothe magnetic disc apparatus; a read/write control part which performsreading and writing of data from/to the magnetic disc; a command recordstoring means for storing the record of the command when receiving thecommand from the host apparatus; a command continuity detecting meansfor detecting continuity of the received commands from the receivedcommands and the command record in the command record storing means atthe receiving of the commands; positional information storing means forstoring the positional information indicating the physical position onthe magnetic disc at which the data on the magnetic disc exists, towhich data the command the continuity of which is detected by thecommand continuity detecting means accesses; and a control part whichperforms a seek control to the magnetic head which is used for accessingto the data, and gives a reading instruction and a writing instructionfor the data on the magnetic disc to the read/write control part beforereceiving the command from the host apparatus.

According to the present invention, even for the accesses to the largecapacity successive file of plural systems on a magnetic disc, whetherthe record of commands are stored so that whether the accesses aresuccessive or not is detected, and when the continuity of plural systemsare detected, the positional information indicating the physicalposition on the magnetic disc of the data on the magnetic disc which isaccessed for respective systems is held, the system to which next accessis requested from the host apparatus is predicted from the commandrecord, and the processing for performing accessing to the data of thepredicted system is started before the command is received. Therefore,the time from the completion of an access to one system to the start ofan access to the next system is shortened, thereby the data transferefficiency between the host apparatus and the magnetic disc apparatus isenhanced.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating the basic construction of amagnetic disc apparatus according to the present invention.

FIG. 2 is an operation diagram in case where accessing is performedsimultaneously to two systems of large capacity successive dataaccording to a first embodiment of the present invention.

FIG. 3 is an operation diagram in case where accessing is performedsimultaneously to two systems of large capacity successive dataaccording to a second embodiment of the present invention.

FIG. 4 is an operation diagram in case where accessing is performedsimultaneously to two systems of large capacity successive dataaccording to a third embodiment of the present invention.

FIG. 5 is an operation diagram in case where accessing is performedsimultaneously to two systems of large capacity successive data and theprediction is erroneously performed according to a fourth embodiment ofthe present invention.

FIG. 6 is an operation diagram in case where accessing is performedsimultaneously to two systems of large capacity successive data and theprediction is erroneously performed according to a fifth embodiment ofthe present invention.

FIG. 7 is an operation diagram in case where accessing is performedsimultaneously to two systems of large capacity successive data in aconventional magnetic disc apparatus.

FIG. 8 is a drawing illustrating commands concerning an operation of theconventional magnetic disc apparatus in case where accessing isperformed simultaneously to two systems of large capacity successivedata.

BEST MODE TO EXECUTE THE INVENTION

Hereinafter, embodiments of the present invention will be described withreference to the drawings. The embodiments as described here are onlyexamples, and it is not necessarily limitted to these embodiments.

Embodiment 1

Initially, an example of a magnetic disc apparatus according the presentinvention will be described as a first embodiment with reference to thedrawings.

FIG. 1 is a block diagram illustrating the construction of a magneticdisc apparatus 9 according to the embodiment of the present invention.In FIG. 1, the magnetic disc apparatus 9 performs data transmissionbetween a host apparatus 1 on receipt of a command (a data accessrequest) issued from the host apparatus 1.

The magnetic disc apparatus includes a host interface part 2 whichcontrols the interface connected to host apparatus 1 and transmitscommands received from the host apparatus 1 to a control section 5, acommand administrating part 3 which stores a command and a commandparameter transmitted from the host apparatus 1, and a command parameterwhich is obtained from calculating the received command parameter andindicates a data access starting position, which is issued in the nextcommand, a position information administrating part 4 which compares anewly received command with a record of commands stored in the commandcontrol part 3 to detect continuity of received commands every time whenit receives a new command from the host apparatus 1, and therebymonitors to which data on the magnetic disc accessing of a command hasbeen performed, and generates and stores the position information(physical cylinder number, head number, and sector number) of data towhich accessing is to be performed first at next accessing from theposition information of data to which accessing was performed at last, acontrol part 5 which compares the content of the command administratingpart 3 with the received command to detect the presence of continuity ofthe received command every time when reception of a command is notifiedfrom the host interface part 2, and controls the whole operation of themagnetic disc apparatus 9 by employing the position information storedin the position information control part 4 when the continuity of thereceived command is detected, a buffer memory 6 which temporarily storesdata transmitted between the host apparatus 1 and the magnetic disc 8,and a read/write control part 7 which executes reading and writingoperation into/from the magnetic disc 8 in response to the instructionfrom the administrating part 5, and the magnetic disc 8.

Hereinafter, a disc access method according to the magnetic discapparatus 9 thus constituted will be described with reference to thedrawings.

FIG. 2 is an exemplary diagram illustrating the disc access methodaccording to the magnetic disc apparatus 9 shown in FIG. 1. Moreparticularly, FIG. 2 illustrates the processing carried out in themagnetic disc apparatus 9 when the host apparatus 1 connected to themagnetic disc apparatus 9 performs accesses to the two systems of largecapacity successive data (hereinafter referred to as “system A” and“system B”) which are located at positions apart from each other in themagnetic disc apparatus 9 simultaneously, in the magnetic disc apparatus9 shown in FIG. 1.

When the host apparatus 1 accesses simultaneously to two large capacitysuccessive data, the host apparatus 1 issues a command for accessingeach file in the large capacity successive data “system A” and a commandfor accessing each file in the large capacity successive data “system B”alternately at a constant period.

The commands for accessing the large capacity successive data of “systemA” and “system B” are stored in the command administrating part 3, andthe control part 5 judges from the contents of the commands stored inthe command administrating part 3 and the content of the commandreceived from the host apparatus 1, that the command received by themagnetic disc apparatus 9 is one for accessing two systems successivedata comprising of “system A” and “system B”.

At first, while accessing to the large capacity successive data ofsystem A is carried out during the period of access 1, the positioninformation to be accessed by the next command to the system A is storedin the position information administrating part 4 and the next commandparameter to the system A is calculated from the data access startingposition and the access data length of the next access to be stored inthe command administrating part 3.

After carrying out the access 1 to system A, the magnetic disc apparatus9 enters a command waiting state until it receives the next command.Subsequently, when it receives the command concerning the access tosystem B, the command administrating part 3 compares the commandparameter at the data access starting position of the received commandwith the command parameter of the data access starting position which iscalculated from the previous command concerning the access to system Band communicates the result to the control section 5.

The operation up to here is described in more detail as follows. Thecommand administrating part 3 calculates, from the received command thecontinuity whereof is recognized and the command parameters of the dataaccess starting position and the access data length which are given fromthe host apparatus 1 together with the received command, the commandparameter indicating the data access starting position for accessing tothat system by the next command and stores the same. This value isobtained as a sum of the data access starting position and the accessdata length.

The position information administrating part 4 monitors to which data onthe magnetic disc the access to the command the continuity whereof isdetected has been performed, and calculates the position information ofthe data which is to be accessed first by the next access from theposition information (physical cylinder number, head number, and thesector number) of the data finally accessed and stores the same.

When receiving a command for accessing the large capacity successivedata next, the command administrating part 3 compares the data accessstarting position command parameter of the received command with thedata access starting position command parameter which was calculatedfrom the command previously received, and notifies the result to theadministrating part 5.

When the comparison results coincide with each other, the controlsection 5 seeks the magnetic head to a track at which the data existsusing the position information which is stored in the positioninformation administrating part 4, and thereafter, instructs theread/write control section 7 to start an access to system B.

Then, while accessing to the large capacity successive data of system Bis carried out during the period of access 2, the position informationof system B to be accessed by the next command to system B is stored inthe position information administrating part 4 and the next commandparameter to system B is calculated from the data access startingposition and the access data length of the next access to be stored inthe command administrating part 3.

In this way, the time from the receiving of the command to the startingof a seek to a track as a target while performing an access to the largecapacity successive data on the magnetic track 8 can be reduced.

As a result, it is possible to secure a bandwidth required for the hostapparatus 1 with shortening the time required for securing the datatransfer capability region for transfer of large capacity successivedata on the buffer memory 6 thereby not resulting in reducing the datatransfer efficiency between the magnetic disc 8 and the buffer memory 6.

In addition, when a magnetic disc apparatus which can apply theabove-described method is constituted, an apparatus that can result thesame effects is obtained, and when the above-described method isrecorded in a recording medium as a program, a recording medium whichhas recorded a disc access control program for a magnetic disc apparatustherein and has the same effects can be obtained.

Embodiment 2

Next, a disc access method for a magnetic disc apparatus which isconstructed to seek the magnetic head without waiting the next commandat completing the data access will be described as a second embodimentwith reference to the drawings.

FIG. 3 is an exemplary diagram illustrating the disc access methodaccording to the magnetic disc apparatus 9 shown in FIG. 1. Moreparticularly, FIG. 3 illustrates the processing carried out in themagnetic disc apparatus 9 when the host apparatus 1 connected to themagnetic disc apparatus 9 is performing accessing to the two systems oflarge capacity successive data (hereinafter referred to a s “system A”and “system B”) which a re located at positions apart from each other inthe magnetic disc apparatus 9 simultaneously, in the magnetic discapparatus 9 shown in FIG. 1.

When the host apparatus 1 accesses simultaneously to two large capacitysuccessive data, the host apparatus 1 issues a command for accessingeach file in the large capacity successive data “system A” and a commandfor accessing each file in the large capacity successive data “system B”alternately at a constant period.

The commands for accessing the large capacity successive data of “systemA” and “system B” are stored in the command administrating part 3, andthe control part 5 judges from the contents of the commands stored inthe command administrating part 3 and the content of the commandreceived from the host apparatus 1, that the command received by themagnetic disc apparatus 9 is one for accessing two systems successivedata comprising of “system A” and “system B”.

At first, while accessing to the large capacity successive data ofsystem A is carried out during the period of access 1, the positioninformation to be accessed by the next command to the system A is storedin the position information administrating part 4 and the next commandparameter to the system A is calculated from the data access startingposition and the access data length of the next access to be stored inthe command administrating part 3.

While after carrying out the access 1 to system A, the magnetic discapparatus 9 enters a command waiting state until it receives the nextcommand, the control section 5 predicts the system B as a system to beaccessed next, and makes the magnetic head seek the track indicated bythe position information of system B which is stored in the positioninformation administrating part 4 (referred as system B seek).

The operation up to here is described in more detail as follows. Thecommand administrating part 3 calculates, from the received command thecontinuity whereof is recognized and the command parameters of the dataaccess starting position and the access data length which are given fromthe host apparatus 1 together with the received command, the commandparameter indicating the data access starting position for accessing tothat system by the next command and stores the same. This value isobtained as a sum of the data access starting position and the accessdata length.

The position information administrating part 4 monitors to which data onthe magnetic disc the access to the command the continuity whereof isdetected has been performed, and calculates the position information ofthe data which is to be accessed first by the next access from theposition information (physical cylinder number, head number, and thesector number) of the data finally accessed and stores the same.

When the access to the system in the magnetic disc 8 being performed iscompleted, the control section 5 predicts the system which is to beaccessed next from the command record which is stored in the commandadministrating part 3 and makes the magnetic head seek the trackindicated by the position information of the predicted system which isstored in the position information administrating part 4.

After the completion of the seek operation by the control part 5, whenreceiving the command for accessing the large capacity successive data,the command administrating part 3 compares the data access startingposition command parameter of the received command with the data accessstarting position command parameter which was calculated from thecommand previously received, and notifies the result to theadministrating part 5.

When the comparison results coincide with each other, the controlsection 5 instructs the read/write control section 7 to access to atrack at which the target data exists using the position informationstored in the position information administrating part 4, thereby tostart accessing to system B.

Then, while accessing to the large capacity successive data of system Bis carried out during the period of access 2, the position informationof system B to be accessed by the next command to system B is stored inthe position information administrating part 4 and the next commandparameter to system B is calculated from the data access startingposition and the access data length of the next access to be stored inthe command administrating part 3.

While, after completing the access 2 to system B, the magnetic discapparatus 9 enters the command waiting state, the control part 5predicts the system A as a system to be accessed next from the commandrecord stored in the command administrating part 3 before receiving thecommand, and makes the magnetic head seek the track indicated by theposition information of the predicted system A which is stored in theposition information administrating part 4 (referred as system A seek).

In this way, the time from the receiving of the command to actuallystarting an access to data when performing accessing to the largecapacity successive data on the magnetic track 8 can be reduced.

As a result, it is possible to secure a bandwidth required for the hostapparatus 1 with shortening the time required for securing the datatransfer capability region for transfer of large capacity successivedata on the buffer memory 6 thereby not resulting in reducing the datatransfer efficiency between the magnetic disc 8 and the buffer memory 6.

In addition, when a magnetic disc apparatus which can apply theabove-described method is constituted, an apparatus that can result thesame effects is obtained, and when the above-described method isrecorded in a recording medium as a program, a recording medium whichhas recorded a disc access control program for a magnetic disc apparatustherein and has the same effects can be obtained.

Embodiment 3

Next, a disc access method for a magnetic disc apparatus which isconstructed to start accessing to a magnetic disc on which data which ispredicted to be accessed by the next command without waiting the nextcommand at completing the data access will be described as a thirdembodiment with reference to the drawings.

FIG. 4 is an exemplary diagram illustrating the disc access methodaccording to the magnetic disc apparatus 9 shown in FIG. 1. Moreparticularly, FIG. 4 illustrates the processing carried out in themagnetic disc apparatus 9 when the host apparatus 1 connected to themagnetic disc apparatus 9 is performing accessing to the two systems oflarge capacity successive data (hereinafter referred to as “system A”and “system B”) which are located at positions apart from each other inthe magnetic disc apparatus 9 simultaneously, in the magnetic discapparatus 9 shown in FIG. 1.

When the host apparatus 1 accesses simultaneously to two large capacitysuccessive data, the host apparatus 1 issues a command for accessingeach file in the large capacity successive data “system A” and a commandfor accessing each file in the large capacity successive data “system B”alternately at a constant period.

The commands for accessing the large capacity successive data of “systemA” and “system B” are stored in the command administrating part 3, andthe control part 5 judges from the contents of the commands stored inthe command administrating part 3 and the content of the commandreceived from the host apparatus 1, that the command received by themagnetic disc apparatus 9 is one for accessing two systems successivedata comprising of “system A” and “system B”.

At first, while accessing to the large capacity successive data ofsystem A is carried out during the period of access 1, the positioninformation to be accessed by the next command to the system A is storedin the position information administrating part 4 and the next commandparameter to the system A is calculated from the data access startingposition and the access data length of the next access to be stored inthe command administrating part 3.

While after carrying out the access 1 to system A, the magnetic discapparatus 9 enters a command waiting state until it receives the nextcommand, the control section 5 predicts the system B as a system to beaccessed next, and makes the magnetic head seek the track indicated bythe position information of system B which is stored in the positioninformation administrating part 4 (referred as system B seek). Aftercompleting the seeking operation, it instructs the read/write controlpart 7 to perform accessing to the data indicated by the positioninformation stored in the position information administrating part 4(referred as system B access 2).

The operation up to here is described in more detail as follows. Thecommand administrating part 3 calculates, from the received command thecontinuity whereof is recognized and the command parameters of the dataaccess starting position and the access data length which are given fromthe host apparatus 1 together with the received command, the commandparameter indicating the data access starting position for accessing tothat system by the next command and stores the same. This value isobtained as a sum of the data access starting position and the accessdata length.

The position information administrating part 4 monitors to which data onthe magnetic disc the access to the command the continuity whereof isdetected has been performed, and calculates the position information ofthe data which is to be accessed first by the next access from theposition information (physical cylinder number, head number, and thesector number) of the data finally accessed and stores the same.

When the access to the system in the magnetic disc 8 being performed iscompleted, the control section 5 predicts the system which is to beaccessed next from the command record which is stored in the commandadministrating part 3 and makes the magnetic head seek the trackindicated by the position information of the predicted system which isstored in the position information administrating part 4.

After the completion of the seek operation by the control part 5, itinstructs the read/write control part 7 to perform an access to the dataindicated by the position information stored in the position informationadministrating part 4.

When a command for accessing a large capacity successive data isreceived, the command administrating part 3 compares the data accessstarting position command parameter of the received command with thedata access starting position command parameter which was calculatedfrom the command previously received, and notifies the result to thecontrol section 5.

When the comparison results coincide with each other, the controlsection 5 instructs the read/write control section 7 to extend theaccessing now being performed if the access data length of the receivedcommand is larger than the access data length of the access which is nowbeing performed. If the access data length of the received command isshorter than the access data length of the access which is now beingperformed, it processes the data length of the access data requested bythe receiving command as an effective data length and stores theposition information of the next data successive to the effective dataon the magnetic disc 8. Then, when the accessing oh the requested datalength is ended, it instructs the read/write control part 7 to concludethe accessing.

Then, while accessing to the large capacity successive data of system Bis carried out during the period of access 2, the position informationof system B to be accessed by the next command to system B is stored inthe position information administrating part 4 and the next commandparameter to system B is calculated from the data access startingposition and the access data length of the next access to be stored inthe command administrating part 3.

While, after completing the access 2 to system B, the magnetic discapparatus 9 enters the command waiting state, the control part 5predicts the system A as a system to be accessed next from the commandrecord stored in the command administrating part 3 before receiving thecommand, and makes the magnetic head seek the track indicated by theposition information of the predicted system A which is stored in theposition information administrating part 4 (referred as system A seek).After completing the seeking operation, it instructs the read/writecontrol part 7 to perform accessing to the data indicated by theposition information stored in the position information administratingpart 4 (referred as system A access 2).

In this way, the time from the receiving of the command to actuallyconcluding the data access when performing accessing to the largecapacity successive data on the magnetic track 8 can be reduced.

As a result, it is possible to secure a bandwidth required for the hostapparatus 1 with shortening the time required for securing the datatransfer capability region for transfer of large capacity successivedata on the buffer memory 6 thereby not resulting in reducing the datatransfer efficiency between the magnetic disc 8 and the buffer memory 6.

In addition, when a magnetic disc apparatus which can apply theabove-described method is constituted, an apparatus that can result thesame effects is obtained, and when the above-described method isrecorded in a recording medium as a program, a recording medium whichhas recorded a disc access control program for a magnetic disc apparatustherein and has the same effects can be obtained.

Embodiment 4

Next, a disc access method for a magnetic disc apparatus which isconstructed to stop the seek operation when the content of the commandwhich is newly issued is not an access which is previously predictedduring the seeking operation in the above-described second and thirdembodiments will be described as a fourth embodiment with reference tothe drawings.

FIG. 5 is an exemplary diagram illustrating the disc access methodaccording to the magnetic disc apparatus 9 shown in FIG. 1. Moreparticularly, FIG. 5 illustrates the processing carried out in themagnetic disc apparatus 9 when the host apparatus 1 connected to themagnetic disc apparatus 9 is performing accessing to the two systems oflarge capacity successive data (hereinafter referred to as “system A”and “system B”) which are located at positions apart from each other inthe magnetic disc apparatus 9 simultaneously, in the magnetic discapparatus 9 shown in FIG. 1.

When the host apparatus 1 accesses simultaneously to two large capacitysuccessive data, the host apparatus 1 issues a command for accessingeach file in the large capacity successive data “system A” and a commandfor accessing each file in the large capacity successive data “system B”alternately at a constant period.

The commands for accessing the large capacity successive data of “systemA” and “system B” are stored in the command administrating part 3, andthe control part 5 judges from the contents of the commands stored inthe command administrating part 3 and the content of the commandreceived from the host apparatus 1, that the command received by themagnetic disc apparatus 9 is one for accessing two systems successivedata comprising of “system A” and “system B”.

At first, while accessing to the large capacity successive data ofsystem A is carried out during the period of access 1, the positioninformation to be accessed by the next command to the system A is storedin the position information administrating part 4 and the next commandparameter to the system A is calculated from the data access startingposition and the access data length of the next access to be stored inthe command administrating part 3.

While after carrying out the access 1 to system A, the magnetic discapparatus 9 enters a command waiting state until it receives the nextcommand, the control section 5 predicts the system B as a system to beaccessed next, and makes the magnetic head seek the track indicated bythe position information of system B which is stored in the positioninformation administrating part 4 (referred as system B seek).

When, while performing a seeking operation to system B, a command foraccessing to the large capacity successive data of system C, the commandadministrating part 3 compares the data access starting position commandparameter of the received command with the data access starting positioncommand parameter calculated from the previous command, and notifies theresult to the control section 5.

The operation up to here is described in more detail as follows. Thecommand administrating part 3 calculates, from the received command thecontinuity whereof is recognized and the command parameters of the dataaccess starting position and the access data length which are given fromthe host apparatus 1 together with the received command, the commandparameter indicating the data access starting position for accessing tothat system by the next command and stores the same. This value isobtained as a sum of the data access starting position and the accessdata length.

The position information administrating part 4 monitors to which data onthe magnetic disc the access to the command the continuity whereof isdetected has been performed, and calculates the position information ofthe data which is to be accessed first by the next access from theposition information (physical cylinder number, head number, and thesector number) of the data finally accessed and stores the same.

When the access to the system in the magnetic disc 8 being performed iscompleted, the control section 5 predicts the system which is to beaccessed next from the command record which is stored in the commandadministrating part 3 and makes the magnetic head seek the trackindicated by the position information of the predicted system which isstored in the position information administrating part 4.

During the seeking operation controlled by the control section 5, whenthe command for accessing the large capacity successive data isreceived, the command administrating part 3 compares the data accessstarting position command parameter of the received command with thedata access starting position command parameter which was calculatedfrom the command previously received, and notifies the result to thecontrol section 5.

When the comparison results do not coincide with each other, the controlsection 5 immediately stops the seeking operation that is now beingperformed, and starts usual command processing to the received command.

In this way, even when a prediction for a next access is erroneouslyperformed while performing accessing to the large capacity successivedata on a magnetic disc 8, an increase in the accessing time can bereduced.

In addition, when a magnetic disc apparatus which can apply theabove-described method is constituted, an apparatus that can result thesame effects is obtained, and when the above-described method isrecorded in a recording medium as a program, a recording medium whichhas recorded a disc access control program for a magnetic disc apparatustherein and has the same effects can be obtained.

Embodiment 5

Next, a disc access method for a magnetic disc apparatus which isconstructed to halt once the data access when the content of the newlyissued command is not an access which was previously predicted whileperforming the data access that is performed in the magnetic discapparatus in the above-described third embodiment will be described as afifth embodiment with reference to the drawings.

FIG. 6 is an exemplary diagram illustrating the disc access methodaccording to the magnetic disc apparatus 9 shown in FIG. 1. Moreparticularly, FIG. 6 illustrates the processing carried out in themagnetic disc apparatus 9 when the host apparatus 1 connected to themagnetic disc apparatus 9 is performing accessing to the two systems oflarge capacity successive data (hereinafter referred to as “system A”and “system B”) which are located at positions apart from each other inthe magnetic disc apparatus 9 simultaneously, in the magnetic discapparatus 9 shown in FIG. 1.

When the host apparatus 1 accesses simultaneously to two large capacitysuccessive data, the host apparatus 1 issues a command for accessingeach file in the large capacity successive data “system A” and a commandfor accessing each file in the large capacity successive data “system B”alternately at a constant period.

The commands for accessing the large capacity successive data of “systemA” and “system B” are stored in the command administrating part 3, andthe control part 5 judges from the contents of the commands stored inthe command administrating part 3 and the content of the commandreceived from the host apparatus 1, that the command received by themagnetic disc apparatus 9 is one for accessing two systems successivedata comprising of “system A” and “system B”.

At first, while accessing to the large capacity successive data ofsystem A is carried out during the period of access 1, the positioninformation to be accessed by the next command to the system A is storedin the position information administrating part 4 and the next commandparameter to the system A is calculated from the data access startingposition and the access data length of the next access to be stored inthe command administrating part 3.

While after carrying out the access 1 to system A, the magnetic discapparatus 9 enters a command waiting state until it receives the nextcommand, the control section 5 predicts the system B as a system to beaccessed next, and makes the magnetic head seek the track indicated bythe position information of system B which is stored in the positioninformation administrating part 4 (referred as system B seek). Aftercompleting the seeking operation, it instructs the read/write controlpart 7 to perform accessing to the data indicated by the positioninformation stored in the position information administrating part 4(referred as system B access 2).

When a command for accessing the large capacity successive data ofsystem C during performing accessing to system B controlled by theread/write control part 7, the command administrating part 3 comparesthe data access starting position command parameter of the receivedcommand with the data access starting position command parameter of thepreviously received command, and notifies the result to the controlsection 5.

Then, when the comparison results do not coincide with each other, thecontrol section 5 immediately halts the accessing operation which is nowbeing performed and starts usual command processing to the receivedcommand.

In this way, even when a prediction for the next access is erroneouslyperformed while performing an access to the large capacity successivedata on the magnetic disc 8, an increase in the accessing time can beavoided.

In addition, when a magnetic disc apparatus which can apply theabove-described method is constituted, an apparatus that can result thesame effects is obtained, and when the above-described method isrecorded in a recording medium as a program, a recording medium whichhas recorded a disc access control program for a magnetic disc apparatustherein and has the same effects can be obtained.

Applicability In Industry

According to a magnetic disc apparatus, a disc access method for amagnetic disc apparatus, and a recording medium for recording a magneticdisc apparatus disc access control program according to the presentinvention, even when the access to the large capacity successive data ofplural systems is performed, the data transfer efficiency between themagnetic disc and the buffer memory can be enhanced, being appropriatefor such as a large capacity memory apparatus of a computer systemcontrolling and administrating the OA apparatuses or industrialapparatuses.

What is claimed is:
 1. A magnetic disc apparatus which can read out orwrite into various kinds of information data by accessing a magneticdisc employed as a recording medium, wherein when a host apparatusconnected externally to the magnetic disc apparatus, performs an accessto each of plural systems constituting large capacity successive data,which systems are located apart from each other in the magnetic discapparatus, the magnetic disc apparatus stores a record of commands atthe same time when the host apparatus issues commands for accessing therespective systems to the magnetic disc apparatus, compares a newreceived command with the stored record of commands to detect continuityof commands against the respective systems every time when it receives anew command issued from the host apparatus, and preserves locationinformation indicating physical location on the magnetic disc at whichdata to be accessed for each of the plural systems locate, and in whicha magnetic disc apparatus, a system preserving the location informationstarts data accessing to the magnetic disc by employing the locationinformation when the magnetic disc apparatus receives a command issuedfrom the host apparatus.
 2. A magnetic disc apparatus which can read outor write into various kinds of information data by accessing a magneticdisc employed as a recording medium, wherein when a host apparatusconnected externally to the magnetic disc apparatus, performs an accessto each of plural systems constituting large capacity successive data,which systems are located apart from each other in the magnetic discapparatus, the magnetic disc apparatus stores a record of commands atthe same time when the host apparatus issues commands for accessing therespective systems to the magnetic disc apparatus, compares a newreceived command with the stored record of commands to detect continuityof commands against the respective systems every time when it receives anew command issued from the host apparatus, and seeks a magnetic heademployed in data access, to a track on the magnetic disc at which dataof a system which is supposed to be accessed by the next command locate,without waiting receiving of the next command when the host apparatusthe data on the magnetic disc at which the respective system datalocate.
 3. A magnetic disc apparatus which can read out or write intovarious kinds of information data by accessing a magnetic disc employedas a recording medium, wherein when a host apparatus connectedexternally to the magnetic disc apparatus, performs an access to each ofplural systems constituting large capacity successive data, whichsystems are located apart from each other in the magnetic discapparatus, the magnetic disc apparatus stores a record of commands atthe same time when the host apparatus issues commands for accessing therespective systems to the magnetic disc apparatus, compares a newreceived command with the stored record of commands to detect continuityof commands against the respective systems every time when it receives anew command issued from the host apparatus, and performs data access, toa track on the magnetic disc at which data of a system which is supposedto be accessed by the next command locate, without waiting receiving ofthe next command when the host apparus accesses the data on the magneticdisc at which the respective system data locate.
 4. A magnetic discapparatus as defined in claim 2, which stops seeking of a magnetic headto a track on the magnetic disc, in which the predicted system locates,in a case where a command is issued from the host apparatus and thecontent of the command is not an access to data of the system that ispredicted, during the seeking operation that is being performed in themagnetic disc apparatus before receiving the command from the hostapparatus.
 5. A magnetic disc apparatus as defined in claim 3, whichstops accessing to the data on the magnetic disc in which the supposedsystem exists, in a case where a command is issued from the hostapparatus and the content of the command is not an access to data of thesystem that is predicted, during the data accessing that is beingperformed in the magnetic disc apparatus before receiving the commandfrom the host apparatus.
 6. A disc access method for a magnetic discapparatus which apparatus can read out or write into various kinds ofinformation data by accessing a magnetic disc employed as a recordingmedium, wherein when a host apparatus connected externally to themagnetic disc apparatus, performs an access to each of plural systemsconstituting large capacity successive data, which systems are locatedapart from each other in the magnetic disc apparatus, the magnetic discapparatus stores a record of commands at the same time when the hostapparatus issues commands for accessing the respective systems to themagnetic disc apparatus, compares a new received command with the storedrecord of commands to detect continuity of commands against therespective systems every time when it receives a new command issued fromthe host apparatus, and preserves location information indicatingphysical location on the magnetic disc at which data to be accessed foreach of the plural systems locate, and in which a magnetic discapparatus, a system preserving the location information starts dataaccessing to the magnetic disc by employing the location informationwhen the magnetic disc apparatus receives a command issued from the hostapparatus.
 7. A disc access method for magnetic disc apparatus which canread out or write into various kinds of information data by accessing amagnetic disc employed as a recording medium, wherein when a hostapparatus connected externally to the magnetic disc apparatus, performsan access to each of plural systems constituting large capacitysuccessive data, which systems are located apart from each other in themagnetic disc apparatus, the magnetic disc apparatus stores a record ofcommands at the same time when the host apparatus issues commands foraccessing the respective systems to the magnetic disc apparatus,compares a new received command with the stored record of commands todetect continuity of commands against the respective systems every timewhen it receives a new command issued from the host apparatus, and seeksa magnetic head employed in data access, to a track on the magnetic discat which data of a system which is supposed to be accessed by the nextcommand locate, without waiting receiving of the next command when thehost appartus accesses the data on the magnetic disc at which therespective system data locate.
 8. A disc access method for a magneticdisc apparatus which can read out or write into various kinds ofinformation data by accessing a magnetic disc employed as a recordingmedium, wherein when a host apparatus connected externally to themagnetic disc apparatus, performs an access to each of plural systemsconstituting large capacity successive data, which systems are locatedapart from each other in the magnetic disc apparatus, the magnetic discapparatus stores a record of commands at the same time when the hostapparatus issues commands for accessing the respective systems to themagnetic disc apparatus, compares a new received command with the storedrecord of commands to detect continuity of commands against therespective systems every time when it receives a new command issued fromthe host apparatus, and performs data access, to a track on the magneticdisc at which data of a system which is supposed to be accessed by thenext command locate, without waiting receiving of the next command whenthe host apparatus accesses the data on the magnetic disc at which therespective system data locate.
 9. A disc access method as defined inclaim 7, which stops seeking of a magnetic head to a track on themagnetic disc, in which the predicted system locates, in a case where acommand is issued from the host apparatus and the content of the commandis not an access to data of the system that is predicted, during theseeking operation that is being performed in the magnetic disc apparatusbefore receiving the command from the host apparatus.
 10. A disc accessmethod for a magnetic disc apparatus as defined in claim 8, which stopsaccessing to the data on the magnetic disc in which the supposed systemexists, in a case where a command is issued from the host apparatus andthe content of the command is not an access to data of the system thatis predicted, during the data accessing that is being performed in themagnetic disc apparatus before receiving the command from the hostapparatus.
 11. A recording medium having recorded a magnetic discrecording apparatus control program, which has recorded a programconcerning a disc access method for a magnetic disc apparatus, whichapparatus can read out or write into various kinds of information databy accessing a magnetic disc employed as a recording medium, whereinwhen a host apparatus connected externally to the magnetic discapparatus, performs an access to each of plural systems constitutinglarge capacity successive data, which systems are located apart fromeach other in the magnetic disc apparatus, the magnetic disc apparatusstores a record of commands at the same time when the host apparatusissues commands for accessing the respective systems to the magneticdisc apparatus, compares a new received command with the stored recordof commands to detect continuity of commands against the respectivesystems every time when it receives a new command issued from the hostapparatus, and in which a magnetic disc apparatus, preserves locationinformation indicating physical location on the magnetic disc at whichdata to be accessed for each of the plural systems locate, and in whicha magnetic disc apparatus, a system preserving the location informationstarts data accessing to the magnetic disc by employing the locationinformation when the magnetic disc apparatus receives a command issuedfrom the host apparatus.
 12. A recording medium having recorded amagnetic disc apparatus control program, which has recorded a programconcerning a disc access method for a magnetic disc apparatus, whichapparatus can read out or write into various kinds of information databy accessing a magnetic disc employed as a recording medium, whereinwhen a host apparatus connected externally to the magnetic discapparatus, performs an access to each of plural systems constitutinglarge capacity successive data, which systems are located apart fromeach other in the magnetic disc apparatus, the magnetic disc apparatusstores a record of commands at the same time when the host apparatusissues commands for accessing the respective systems to the magneticdisc apparatus, compares a new received command with the stored recordof commands to detect continuity of commands against the respectivesystems every time when it receives a new command issued from the hostapparatus, and seeks a magnetic head employed in data access, to a trackon the magnetic disc at which data of a system which is supposed to beaccessed by the next command locate, without waiting receiving of thenext command when the host apparatus accesses the data on the magneticdisc at which the respective system data locate.
 13. A recording mediumhaving recorded a magnetic disc apparatus control program, which hasrecorded a program concerning a disc access method for a magnetic discapparatus, which apparatus can read out or write into various kinds ofinformation data by accessing a magnetic disc employed as a recordingmedium, wherein when a host apparatus connected externally to themagnetic disc apparatus, performs an access to each of plural systemsconstituting large capacity successive data, which systems are locatedapart from each other in the magnetic disc apparatus, the magnetic discapparatus stores a record of commands at the same time when the hostapparatus issues commands for accessing the respective systems to themagnetic disc apparatus, compares a new received command with the storedrecord of commands to detect continuity of commands against therespective systems every time when it receives a new command issued fromthe host apparatus, and performs data access, to a track on the magneticdisc at which data of a system which is supposed to be accessed by thenext command locate, without waiting receiving of the next command whenthe host apparatus accesses the data on the magnetic disc at which therespective system data locate.
 14. A recording medium having recorded amagnetic disc apparatus control program, which has recorded a programconcerning a disc access method for a magnetic disc apparatus, of claim12, which stops seeking of a magnetic head to a track on the magneticdisc, in which the predicted system locates, in a case where a commandis issued from the host apparatus and the content of the command is notan access to data of the system that is predicted, during the seekingoperation that is being performed in the magnetic disc apparatus beforereceiving the command from the host apparatus.
 15. A recording mediumhaving recorded a magnetic disc apparatus control program, which hasrecorded a program concerning a disc access method for a magnetic discapparatus, of claim 13, which stops accessing to the data on themagnetic disc in which the supposed system exists, in a case where acommand is issued from the host apparatus and the content of the commandis not an access to data of the system that is predicted, during thedata accessing that is being performed in the magnetic disc apparatusbefore receiving the command from the host apparatus.
 16. A magneticdisc apparatus which can read out or write into various kinds ofinformation data by accessing a magnetic disc employed as a recordingmedium, which comprises: a buffer memory which can store a plurality ofdata per one command which is transferred between the host apparatus andthe magnetic disc apparatus in response to the commands issued from thehost apparatus which is connected externally to the magnetic discapparatus; a read/write control part which performs reading and writingof data from/to the magnetic disc; a command record storing means forstoring the record of the command when receiving the command from thehost apparatus; a command continuity detecting means for detectingcontinuity of the received commands from the host apparatus and thecommand record in the command record storing means at the receiving ofthe commands; positional information storing means for storing thepositional information indicating the physical position on the magneticdisc at which the data on the magnetic disc exists, to which data thecommand the continuity of which is detected by the command continuitydetecting means accesses; and a control part which performs a seekcontrol to the magnetic head which is used for accessing to the data,and gives a reading instruction and a writing instruction for the dataon the magnetic disc to the read/write control part before receiving thecommand from the host apparatus.
 17. A magnetic disc apparatus asdefined in claim 3, which stops seeking of a magnetic head to a track onthe magnetic disc, in which the predicted system locates, in a casewhere a command is issued from the host apparatus and the content of thecommand is not an access to data of the system that is predicted, duringthe seeking operation that is being performed in the magnetic discapparatus before receiving the command from the host apparatus.
 18. Adisc access method as defined in claim 8, which stops seeking of amagnetic head to a track on the magnetic disc, in which the predictedsystem locates, in a case where a command is issued from the hostapparatus and the content of the command is not an access to data of thesystem that is predicted, during the seeking operation that is beingperformed in the magnetic disc apparatus before receiving the commandfrom the host apparatus.
 19. A recording medium having recorded amagnetic disc apparatus control program, which has recorded a programconcerning a disc access method for a magnetic disc apparatus, of claim13, which stops seeking of a magnetic head to a track on the magneticdisc, in which the predicted system locates, in a case where a commandis issued from the host apparatus and the content of the command is notan access to data of the system that is predicted, during the seekingoperation that is being performed in the magnetic disc apparatus beforereceiving the command from the host apparatus.